AceShowbiz - Just a day after Kensington Palace announced Meghan Markle's pregnancy, Kate Middleton is preparing to become an aunt to another baby. Her heavily pregnant sister Pippa Middleton could go into labor any minute now and she has checked into hospital as her due date approaches.

The 35-year-old socialite and author was spotted arriving at the highly-renowned Lindo Wing at St. Mary's Hospital on Monday morning, October 15, followed by her husband James Matthews who carried what appeared to be two overnight bags. The Lindo Wing is the same maternity ward where Kate, the Duchess of Cambridge, delivered her three children Prince George, Princess Charlotte and Prince Louis.

Pippa was reportedly smiling as she entered the maternity unit wearing a long blue coat, white shoes and sunglasses. Her businessman husband, meanwhile, sported a blue shirt, a dark blue sweater, jeans and brown shoes.

Pippa confirmed her pregnancy in June, a year after she and James tied the knot on May 20, 2017. She announced the news through a column for Waitrose Kitchen magazine, sharing how she had to adjust her exercise routine, "When I learned the happy news that I was pregnant, I realized I needed to adjust my four to five-day-a-week [fitness] routine."

The younger sister of Kate Middleton, however, did not suffer from morning sickness during her first trimester. "I was lucky to pass the 12 week scan without suffering from morning sickness. That meant I was able to carry on as normal," she wrote at the time.

Pippa made a surprising appearance at Princess Eugenie and Jack Brooksbank's wedding on Friday, October 12. Nine months pregnant, she was predicted to skip the most recent royal wedding, though she and the newlywed couple was close enough that Eugenie and Jack attended her and James' 2017 wedding. Pippa dressed her baby bump in a dark green, midi length, long sleeve dress with matching fascinator.